This invention relates to the field of distributorless electronic ignition systems and, more particularly, to the accurate determination of the proper cylinder to be fired at each spark pulse.
With the transition from mechanical devices for coupling an ignition coil to the spark plugs of an internal combustion engine to electronic (distributorless) circuits has come the problem of identifying the crankshaft position and being certain that the proper cylinder or cylinders are fired at each spark pulse. It is also desirable to continually update the position information. It is also important to provide the widest possible range of spark advance in such a system.
Many different combinations of sensors with sensible or detectable elements on the crankshaft or flywheel of an internal combustion engine have been utilized for the purpose of determining crankshaft position and speed of rotation. One such arrangement has utilized three tabs or projections on the flywheel, two being spaced 180.degree. apart and the third spaced 72.degree. ahead of one of those two. Two sensors are spaced adjacent the flywheel edge and 72.degree. apart. It is then apparent that each sensor will output three pulses per revolution, and that only once per revolution will there be simultaneous output pulses. While these sensor outputs could be used in many ways, it is apparent that the two simultaneous or "synchronized" pulses could be used to indicate the correct cylinder to be fired. However, if a very wide range of advance angles is desired, it may be difficult to use the sync pulses for this purpose; e.g. the desired spark time may be later than the sync pulse occurrence.